1. Field of the Invention
This invention relates to a shift control apparatus of an automatic transmission for a vehicle.
2. Description of the Related Art
To provide smooth shift without the raising of the engine rotation speed in shift control of an automatic transmission for a vehicle, particularly at the upshift time, it is important to control the hydraulic pressure of an engagement side clutch (frictional engagement element). Hitherto, various techniques for learning whether or not the shift is good and controlling optimum clutch hydraulic pressure have been proposed.
For example, in an art described in JP-B-3-16545, a temporary rise in the engine speed during shifting is captured and the preparation time and engagement hydraulic pressure for a clutch on the engagement side (frictional engagement element) are corrected.
However, the related art is hard to be satisfactory in the point of preventing the raising of the engine rotation speed.
It is therefore an object of the invention to provide a shift control apparatus of an automatic transmission for a vehicle for performing a learn correction to hydraulic pressure control and effectively preventing the raising of the engine rotation speed.
To the end, according to a first aspect of the invention, there is provided a shift control apparatus of an automatic transmission for a vehicle, comprising a plurality of frictional engagement elements driven by electromagnetic solenoids wherein hydraulic pressure is applied to the frictional engagement element on the engagement side and hydraulic pressure is discharged from the frictional engagement element on the release side for shifting output of an internal combustion engine, the shift control apparatus comprising raising occurrence detection means for determining whether or not raising the rotation speed occurs in the internal combustion engine, engagement hydraulic pressure learn correction means, when the raising occurrence detection means detects raising the rotation speed of the internal combustion engine at a predetermined shifting time, for making a learn correction to the engagement hydraulic pressure of the frictional engagement element on the engagement side at the next predetermined shifting time, and release hydraulic pressure correction means, when the learn correction value of the engagement hydraulic pressure provided by the engagement hydraulic pressure learn correction means becomes a predetermined value or more, for correcting the release hydraulic pressure of the frictional engagement element on the release side at the next predetermined shifting time.
When raising of the rotation speed of the internal combustion engine is detected, a learn correction is made to the engagement hydraulic pressure of the frictional engagement element on the engagement side and when the learn correction value becomes a predetermined value or more, the release hydraulic pressure of the frictional engagement element on the release side is corrected at the next predetermined shifting time. That is, it is assumed that raising of the rotation speed of the internal combustion engine occurs because the hydraulic pressure of the frictional engagement element on the engagement side is low or the startup (preparation time) is late, and the engagement hydraulic pressure is increased or the startup is hastened. When raising of the engine rotation speed still occurs, it is considered that releasing the hydraulic pressure of the frictional engagement element on the release side is early (for example, the friction coefficient of the frictional engagement element is lowered, etc.,), and the hydraulic pressure on the release side is corrected. Thus, an excessive correction of the engagement hydraulic pressure can be prevented and convergence of learning can be enhanced, so that raising of the rotation speed of the internal combustion engine can be prevented effectively.
According to a second aspect of the invention, the shift control apparatus further comprises inertia phase start time appropriateness determination means for detecting the start time of an inertia phase, comparing the start time with a predetermined reference time, and determining whether or not the inertia phase start time is appropriate, and when it is determined that the inertia phase start time is not appropriate, the release hydraulic pressure correction means corrects the release hydraulic pressure of the frictional engagement element on the release side at the next predetermined shifting time.
When it is determined that the inertia phase start time is not appropriate, specifically, early or late and more specifically, late, the release hydraulic pressure of the frictional engagement element on the release side is corrected at the next predetermined shifting time. Thus, an excessive correction of the engagement hydraulic pressure can be prevented and convergence of learning can be enhanced, so that raising of the rotation speed of the internal combustion engine can be prevented effectively.
According to a third aspect of the invention, the shift control apparatus further comprises engagement hydraulic pressure correction means, when raising of the rotation speed of the internal combustion engine is not detected and it is determined that the inertia phase start time is not appropriate at the next predetermined shifting time, for correcting the engagement hydraulic pressure of the frictional engagement element on the engagement side at the next predetermined shifting time.
When raising of the rotation speed of the internal combustion engine is not detected and it is determined that the inertia phase start time is not appropriate, specifically, early or late and more specifically, early, the engagement hydraulic pressure of the frictional engagement element on the engagement side is corrected at the next predetermined shifting time. Thus, an excessive correction of the engagement hydraulic pressure can be prevented and convergence of learning can be enhanced, so that raising of the rotation speed of the internal combustion engine can be prevented effectively.
According to a fourth aspect of the invention, there is provided a shift control apparatus of an automatic transmission for a vehicle, comprising a plurality of frictional engagement elements driven by electromagnetic solenoids wherein hydraulic pressure is applied to the frictional engagement element on the engagement side and hydraulic pressure is discharged from the frictional engagement element on the release side for shifting output of an internal combustion engine, the shift control apparatus comprising raising occurrence detection means for determining whether or not raising the rotation speed occurs in the internal combustion engine, inertia phase start time appropriateness determination means for detecting the start time of an inertia phase, comparing the start time with a predetermined reference time, and determining whether or not the inertia phase start time is appropriate, and release hydraulic pressure correction means, when raising of the rotation speed of the internal combustion engine is detected and it is determined that the inertia phase start time is not appropriate at a predetermined shifting time, for correcting the release hydraulic pressure of the frictional engagement element on the release side at the next predetermined shifting time.
When raising of the rotation speed of the internal combustion engine is detected and it is determined that the inertia phase start time is not appropriate, specifically, early or late and more specifically, early, the release hydraulic pressure of the frictional engagement element on the release side is corrected. That is, it is judged that the inertia start time is early because the engagement hydraulic pressure already high and it is judged that raising of the engine rotation speed is not still canceled because the hydraulic pressure on the release side is low for control. Thus, an excessive correction of the engagement hydraulic pressure can be prevented and convergence of learning can be enhanced, so that raising of the rotation speed of the internal combustion engine can be prevented effectively.
According to a fifth aspect of the invention, the shift control apparatus further comprises engagement hydraulic pressure correction means, when raising of the rotation speed of the internal combustion engine is not detected and it is determined that the inertia phase start time is not appropriate at the next predetermined shifting time, for correcting the engagement hydraulic pressure of the frictional engagement element on the engagement side at the next predetermined shifting time.
When raising of the rotation speed of the internal combustion engine is not detected and it is determined that the inertia phase start time is not appropriate, specifically, early or late and more specifically, late, the engagement hydraulic pressure is corrected. Thus, an excessive correction of the engagement hydraulic pressure can be prevented and convergence of learning can be enhanced, so that raising of the rotation speed of the internal combustion engine can be prevented effectively.